It is sometimes desired to moor a floating ship or other vessel to a buoyant tower in an offshore location for extended or indefinite periods of time. A typical instance of such use arises in conjunction with the operation of an offshore oil well, in which oil from below the surface of the ocean rises through pipes connected to a buoyant tower and into a ship attached thereto. Instead of transporting the oil from the offshore location to a refinery, it has been proposed to moor to the buoyant tower a vessel which is in effect a floating refinery, which can be used to process the crude oil. In such cases, the floating refinery is intended to remain attached to the tower for long periods of time. In order to prevent damage to the ship or the buoyant tower, it is desirable to provide a rigid mooring arm connecting the ship to the tower. The rigid arm must be adequately strong to resist the forces exerted on it by the action of the wind, waves and tide and must at the same time permit the vessel to swing about the mooring point, as well as to roll and pitch. Further, it is desirable that the mooring arm permit the connection between the ship and the tower to be made or broken quickly without damage to either the tower or the ship. In view of the large size of the vessel typically used in such installations, the elements of the mooring system must be large and heavy to withstand the enormous forces which are encountered. The size and weight of the mooring system combined with the size of the vessel, the movement of which must be controlled during the connect and disconnect procedures, create severe problems in the design of a mooring system for insuring that connection and disconnection can be made without collision damage to either the vessel or the tower.